Kinetics of glucose mutarotation was studied in the range 283!308 K in water!isopropanol mixtures with alcohol fractions of 0!20 mol %. In dilute solutions (0!6 mol % of i-PrOH), the process is catalyzed by water exclusively. The water!isopropanol system sharply differs in kinetic behavior from the water!urea system.The present work is a continuation of our research into the effect of the structure and physicochemical properties of aqueous organic solvents on the rates of organic reactions with various mechanisms. In the previous work [1] we discussed the kinetics of spontaneous (solvent-catalyzed) glucose mutarotation in water3urea solutions. It was found that the reaction rate increases with increasing urea fraction in the solvent. In all the aqueous organic solvents used in glucose mutarotation (anomerization) studies {with protic (methanol, ethanol, and tert-butanol) and aprotic solvents (THF, dioxane, DMSO, and acetonitrile) as organic components of the medium; see references in [1]}, the reaction rate invariably decreased with increasing concentration of the organic component. Here we report the kinetics of glucose mutarotation in water3isopropanol mixtures never used before in such studies.The experimental procedure was the same as described in [1]. The kinetics were studied at four temperatures in the range 2833308 K in mixtures containing from 0 to 20 mol % of isopropanol (Table 1). The error in the rate constants was 1.5%. Table 2 lists the effective quasithermodynamic activation parameters of the reversible process (G is glucose):In [1] we showed that these parameters well characterize variation with the medium of the activation parameters of the [direct] reaction described by the constant k 1 (this is particularly valid for the activation enthalpy).The resulting data are useful to discuss in comparison with related data for water3urea [1] and water3tert-butanol mixtures [2]. Comparison of the kinetics of alkaline hydrolysis of esters in these media [3,4] revealed a conspicuous effect of solvent structure and balance between hydrophobic and hydrophilic intermolecular interactions on the reaction rate. The properties of the H 2 O3urea, H 2 O3t-BuOH, and H 2 O3i-PrOH systems are discussed in detail in the monograph [5] and papers [1,3,4,6]. Here it will only be recalled that the H 2 O3t-BuOH systems fea- Table 1. Rate constants of glucose mutarotation in the water!isopropanol system ÄÄÄÄÄÄÄÂÄÄÄÄÄÒÄÄÄÄÄÄÄÂÄÄÄÄÄÒÄÄÄÄÄÄÄÂÄÄÄÄÄ c(i-PrOH),³k 10 5 ,ºc(i-PrOH),³k 10 5 ,ºc(i-PrOH),³k 10 5 , mol % ³ s !1 º mol % ³ s !1 º mol % ³ s !1 1.0 ³ 91.5 º 4.0 ³ 75.5 º 12.0 ³ 58.2 1.5 ³ 89.5 º 5.0 ³ 74.5 º 15.0 ³ 58.0 2.0 ³ 80.7 º 6.0 ³ 72.7 º 20.0 ³ 56.2 ÄÄÄÄÄÄÄÁÄÄÄÄÄÐÄÄÄÄÄÄÄÁÄÄÄÄÄÐÄÄÄÄÄÄÄÁÄÄÄÄÄ

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